brain lab briefing Flashcards
describe the layers of the scalp
Skin: where hair grows, nutrients for hair follicles are found here
Connective tissue: dense subcutaneous layer of fat and fibrous tissue. contains nerves and vessels of scalp.
epicranial Aponeurosis: tough layer of dense connective tissue which runs from frontalis muscle anteriorly to occipitalis posteriorly
Loose connective tissue: areolar connective tissue, made up of random collagen bundles, separates the upper 3 layers of scalp of pericranium, and allows them to move in realign to pericranium.
Periosteum: provides nutrition to the cranium capacity to repair
if there is an infected scalp wound, how is there potential for it to spread intracranially?
via emissary veins into cranial cavity
why is the convex shape of the skull important?
it dissipates injury by distributing and minimising the effects fo a blow to the head so the head is able to take more force without fracturing
what important structures are found the base of the skull?
cranial nerves and blood supply
what bones make up the base of the skull?
orbital plate of frontal bone, sphenoid bone, squamous and petrous temporal bones, occipital bone
describe a depressed skull fracture
bone fragments depress inwards with damage/compression of brain
describe a linear skull fracture
a break in cranial bone resembling a thin line. it occurs at site of impact but the fracture lines radiate away
what is battle’s sign?
bruising over the mastoid process (purplish bruising)
what is periorbital ecchymosis also known as?
raccoon or panda eyes
what causes panda eyes?
basal skull fracture that ruptures meninges and causes venous sinuses to bleed into arachnoid vill and cranial sinuses.
what clinical features are seen in panda eyes beside bruising around the eyes?
blood or csf coming out of the ear or nose which indicates breach of the meninges
what diagnostic test should be carried out if panda eyes are present?
CT scan
what is the pterion?
region of skull behind the temple, where the frontal, parietal, temporal, and sphenoid bones join together.
why is there a high chance of fracture of the pterion and what consequences would a fracture have?
It is translucent and very thin
There are branches of meningeal arteries underneath so fracture could lead to intracranial haematoma.
what are the 2 layers of the dura mater and where are they attached and separated?
endosteal and meningeal layers
they are closely attached and only separate to form venous sinuses and at reflections
what are the 2 main dural reflections and what do reflections do?
falx cerebri and tentroium cerebellum
They divide the cranial cavity into compartments by forming partitions
list 3 types of intracranial haematomas
epidural/extradural
subdural
intracerebral
describe an epidural haematoma including causes and shape
When blood collects between periosteal layer of dura and skull, the blood strips the dura away from the periosteum.
Related to a skull fracture, caused by arterial bleeding usually of middle meningeal artery. It forms a lens shaped swelling because it cannot swell along suture lines
describe a subdural haematoma
when blood collects between dura and arachnoid
Blood is of venous origin = slower bleeding
what features can be seen in an acute extradural/epidural haematoma CT scan?
lens shaped haematoma
“white” area = fresh blood in context of head injury
ventricular shift - swelling of brain closes the ventricles and shifts the ventricle away from midline
what features can be seen in an acute subdural haematoma CT scan?
crescent shaped haematoma as there are no suture limitations so blood can spread all the way around the brain
middling shift of ventricles
what re the 3 components of intracranial volume?
blood, csf, brain
what happens in response to raised cranial pressure due to presence of a mass? what happens I this mass keeps increasing?
compensatory mechanisms eg removing venous blood and csf
after a critical point, there is decompensation which causes ICP to rise rapidly
what is the equation for cerebral perfusion pressure?
CPP = MAP - ICP
